1. Field of the Invention
The present invention relates to an electric microscope and an electric revolver device used in a microscope, etc.
2. Related Background Art
Recently, electrification and automation have been advanced in the field of microscopes, so as to save unnecessary works of an operator other than a observation of a specimen. Particularly, most of high-grade microscopes already have an electrified focusing stage, revolver, or the like. As electric revolter devices suitable for such electric microscopes, there are proposed a revolver device which has a forward-rotation button and a reverse-rotation button provided on a console panel of a microscope so that an objective lens is changed over to an adjacent objective lens one by one by one of these two buttons, a revolver device which on a console panel has buttons respectively corresponding to all of the objective lenses mounted on revolver body so that any of the objective lenses can be directly inserted into an optical path of the microscope by operating the corresponding button or the like.
As objective lenses to be mounted on the revolver body of the microscope, there are proposed an immersion objective lens with a liquid such as water or oil filled in a gap between the tip end of the objective lens and a specimen to be used, and a dry objective lens with nothing to be filled (a gap between the objective lens and a specimen is filled with an air) to be used.
When a specimen is observed by using an immersion objective lens, it is necessary to pour water or oil into a gap between the objective lens and the specimen by a dropping pipette or the like. In this case, if objective lenses are changed over electrically in a conventional microscope, an immersion objective lens is instantly disposed on an optical path. In this condition, a space between the specimen and the immersion objective lens is very small, so that it is difficult to conduct a liquid pouring operation. In such case, it is required, after disposing the immersion objective lens, to widen the space between the objective lens and the specimen by slightly lowering a stage, and then, after dropping the liquid on the specimen, to set the sight by elevating the stage until the liquid reaches the tip end of the objective lens. It is also proposed that only when that an objective lens is changed over to an immersion objective lens, the liquid is poured in the gap between the objective lens and the specimen by manually rotating the revolver, and not by using an electric change-over in accordance with a switch operation.
Also in case that an immersion objective lens is changed over to a dry type objective lens, it is required to remove the liquid filled between the objective lens and the specimen.
However, in the conventional microscope, it is troublesome to conduct an operation of filling or removing the liquid which is to be conducted as described above. Moreover, it is required to conduct a manual operation when the immersion objective lens is used, and an electric operation otherwise, which spoils the advantages of the electrification.
A specific structure of an electric revolver device is disclosed in Japanese Patent Application Laid-Open No. 7-311343. In this electric revolver device, a revolver with a plurality of objective lenses mounted thereon is rotated with a motor, and the final positioning of rotation is mechanically conducted by a click stop mechanism.
The click stop mechanism is composed of a leaf spring provided with a steel ball and a rail with a V-shaped groove. The leaf spring is provided on a retaining member for rotatably retaining the revolver, and the rail is provided on the revolver. The steel ball is pressed against the rail by the leaf spring, and the steel ball is dropped into the V-shaped groove due to this pressing force, so as to position the revolver. In order to conduct this positioning accurately, in the click stop mechanism of the electric revolver device, a pressure larger than that in a manually-operated revolver is applied mechanically.
When the revolver is rotated in a predetermined amount, the brake is electrically applied on the motor. However, a timing of applying the brake is adjusted by the width of a slit plate provided on the revolver, or controlled by an electric delay circuit which delays a detection signal from a photo-interrupter for detecting a slip position of the slit plate.
In the above-mentioned electric revolver device, the V-shaped groove of the click stop mechanism may be abraded or a lubricating oil may run out due to a secular change. Accordingly, for the objective lenses which have been frequently changed over, an overrun or a short-run may occur at the time of positioning.
In order to avoid this, a timing of applying the brake on the motor is adjusted, by adjusting the slit width of the above-mentioned slit plate, or adjusting a delay time caused by the delay circuit. However, such adjustment is effected for all of the objective lenses mounted on the revolver, so that an objective lens requiring no adjustment is affected. As a result, if a precision in positioning each of the objective lenses varies widely, a precise positioning can not be achieved for all of the objective lenses.
Also, it is required to precisely position the revolver at a stop position, a large operational torque (drive force) is required correspondingly to a mechanical pressure of the click stop mechanism, which results in an increased size of the motor to be used. If the size of the motor is increased, the entire size of the revolver device is increased. As disclosed in Japanese Patent Application Laid-Open No. 7-311343, if the motor is received inside the revolver, a center portion of the revolver is protruding, so that it becomes difficult to attach or detach the objective lenses.